1. Field of the Invention
The present invention relates to a gas analyzing apparatus, more particularly to a gas analyzing apparatus capable of analyzing impurities of ppb level to sub-ppb level contained in various kinds of high-purity gases with one analyzer.
2. Description of the Prior Art
In a semiconductor-manufacturing field, since trace impurities in high-purity gas to be used have a bad effect on device performance, it is necessary to observe the trace impurities. As a means for analyzing various kinds of impurities of ppb level to ppt level present in high-purity gas, an apparatus has been used recently where a separator such as a gas chromatography or the like and an analyzer such as an atmospheric pressure ionization mass spectrometer (APIMS) are combined.
In the apparatus where the separator and the analyzer are thus combined, for example, as shown in the systematic diagram of FIG. 4, there are cases where a sample gas supplied from a sample gas source 11 is directly analyzed in the analyzer 12, and the sample gas is also analyzed in the analyzer 12 after major components and impurities of the sample gas are separated in a separator 13. In the above apparatus, it is necessary to introduce a sample gas from the sample gas source by switching to the direction of the analyzer 12 and to the direction of the separator 13 in a first gas switching apparatus 14 of a sample gas inlet side, and at the same time, to introduce the sample gas toward the analyzer 12 by switching to the direction of a direct introduction and to the direction of the separator in a second switching apparatus 15 of a sample gas flowing-out side.
That is to say, when the sample gas is directly analyzed in the analyzer 12, a shut off valve 14a is opened and a shut off valve 14b is closed in the first gas switching apparatus 14 while a shut off valve 15a is opened and a shut off valve 15b is closed in the second gas switching apparatus 15. Furthermore, when the analysis of the sample gas is carried out via the separator 13, the shut off valve 14a is closed and the shut off valve 14b is opened in the first gas switching apparatus 14 while the shut off valve 15a is closed and the shut of valve 15b is opened in the second gas switching apparatus 15. Furthermore, when the separator 13 is not used during the analysis, a carrier gas supplied to the separator 13 from a carrier gas source 16 is exhausted to the outside from an exhaust valve 17 provided in an outlet passage of the separator 13.
However, according to the construction as above-mentioned, two gas switching apparatuses must be used. Moreover, the opening and closing of the shut off valves of both the gas switching apparatuses are required to connectively operate. Furthermore, when the separator 13 is used, since a gas passage between both the gas switching apparatuses becomes a condition that the sample gas is shut up and stays therein, it is impossible to carry out the gas switching swiftly. Furthermore, there is such an occasion that analysis results are badly influenced by adsorption/desorption of the sample gas components to/from an inner surface of piping.
Therefore, the object of the present invention is to provide a gas analyzing apparatus capable of minimizing gas remaining by integrating the gas switching apparatuses into one, and capable of analyzing impurities of ppb level to sub-ppb level contained in various kinds of high-purity gases efficiently and accurately with one analyzer.
To achieve the above object, according to the present invention, there is provided a gas analyzing apparatus comprising a separator such as a gas chromatograph or the like for separating gas components and an analyzer such as an atmospheric-pressure ionization mass spectrometer or the like for analyzing gas components, the gas analyzing apparatus comprising: an analyzer introduction passage for directly introducing a; sample gas supplied from a sample gas source into the analyzer via an analyzer introduction valve; a separator introduction passage diverging from a first side passage of the analyzer introduction valve for introducing a sample gas into the separator via a separator introduction valve; a separator flowing-out passage for introducing the sample gas flowing out from the separator into a second side passage of the analyzer introduction valve via a separator flowing-out valve; and a gas switching apparatus to be such formed that when the analyzer introduction valve is opened, the separator introduction valve and the separator flowing-out valve are connectively operated to be closed, and when the analyzer introduction valve is closed, the separator introduction valve and the separator flowing-out valve are connectively operated to be opened.
In particular, according to the gas analyzing apparatus of the present invention, the gas switching apparatus comprises a purge passage to which a first side passage of said separator flowing-out valve and a second side passage of said separator introduction valve are connected via a purge valve which is opened and closed simultaneously with said analyzer introduction valve.
Furthermore, according to the gas switching apparatus of the present invention, the gas switching apparatus is a 4-connected 4-way valve where respective valves and passages thereof are integrally formed.
Furthermore, according to the present invention, there is provided a gas analyzing apparatus comprising a separator such as a gas chromatograph or the like for separating gas components, an analyzer such as an atmospheric-pressure ionization mass spectrometer or the like for analyzing gas components, a sample gas source for supplying a sample gas, and a carrier gas source for supplying a carrier gas into said separator, said gas analyzing apparatus comprising: a gas switching apparatus comprising: an analyzer introduction passage to which a sample gas passage connected to said sample gas source and an analyzer inlet passage connected to said analyzer are connected via an analyzer introduction valve; a separator introduction passage to which said sample gas passage and a separator inlet passage are connected via a separator introduction valve; a separator flowing-out passage to which a separator outlet passage and said analyzer inlet passage are connected via a separator flowing-out valve; and a purge passage to which said separator outlet passage and a separator inlet passage are connected via a purge valve; wherein said gas switching apparatus is such operated that when said sample gas from said sample gas source is directly introduced into said analyzer, said analyzer introduction valve and said purge valve are opened together while said separator introduction valve and said separator flowing-out valve are closed together thereby said sample gas from said sample gas source is directly introduced into said analyzer via said analyzer introduction passage while a carrier gas supplied from said carrier gas source into said separator and flowing out from said separator outlet passage is introduced into said separator inlet passage via said purge passage, and when said sample gas from said sample gas source is introduced into said analyzer after said sample gas is separated in said separator, said analyzer introduction valve and said purge valve are closed together while said separator introduction valve and said separator flowing-out valve are opened together thereby said sample gas from said sample gas source is introduced into said separator through said separator introduction passage to be separated in said separator and then is accompanied by said carrier gas to flow out from said separator outlet passage and then introduced into said analyzer inlet passage through said separator flowing-out passage.